Lorenz SZ 40
The Lorenz Schlüsselzusatz 40, or SZ 40 for short.
This is a simulation of the regular SZ 40 model with 12 wheels with changeable patterns. It consists of five "spaltencaesar" (Chi) wheels which all stepped in unison for each character enciphered. These drive two "vorgelege" (control / Mu) wheels which then step the five "springcaesar" (Psi) wheels irregularly.
The original pre-production SZ 40 had ten mechanical cipher wheels with fixed peg patterns but this was found to be easily deciphered which led to the development of the regular SZ 40. An experimental link using SZ40 machines was started in June 1941.
Lorenz SZ 42a
The Lorenz Schlüssezusatz 42a.
This is a simulation of the SZ 42a model. The SZ 42 was brought into use from 1942 onwards to improve upon the security of the SZ 40. The 12 wheels are exactly the same as the original model, but an additional limitation was introduced to alter the pattern of the Psi wheels.
Instead of just using the 37-pin motor wheel setting to tell when the Psi wheels should turn, the setting of the second Chi wheel(No.9) from one position back was also checked. If the 37-pin wheel active setting was off and the limitation value from Chi2(1 back) wheel was on, the Psi wheels would not move, any other combination would move the Psi wheels one position.
A further optional limitation, which was based on the fifth impulse from the plaintext character 2 back, was also available which could be added (see KT-Schalter below).
Lorenz SZ 42b
The Lorenz Schlüsselzusatz 42b.
This is a simulation of the SZ 42b model. The SZ 42b again uses the same wheels as it's predecessors, but another wheel was included in the limitation calculation (see SZ 42a).
The limitation was now set as the XOR of the Chi 2 wheel from one step back and the Psi 1 wheel(No.1) also from one step back. This result then set how often the Psi wheels would turn in exactly the same way as described on the SZ 42a.
A further optional limitation, which was based on the fifth impulse from the plaintext character 2 back, was also available which could be added (see KT-Schalter below).
Lorenz SZ 42c
The Lorenz Schlüsselzusatz 42c.
This is a simulation of the Lorenz SZ 42c (also known as sk-44). This was never in production but was being built to replace the SZ42a/b. it was not completed by the time the war ended. The information comes from sparse TICOM reports - I am not aware of any photos or models of this version running so this could be the first time this action has been shown since 1945. There were to be 10 wheels which moved constantly unless interrupted. Interuption of wheels 1-5, which move in unison, was by the settings of wheel 9+10, wheel 6 by 8+2, 7 by 9+3, 8 by 10+4, 9 by 6+5 and 10 by 7+1. Should all wheels become locked together, the machine would count to 3 then step wheels 1 to 5.